JPH0648108A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the eccentric abrasion resistance by suppressing the reduction of the crown R by maintaining the bead durability by setting the radius of curvature of the carcass line in the filled state with a prescribed internal pressure after the rim assembly, carcass height, and the max. width position height. CONSTITUTION:In the filled state with the internal pressure of 10% of a prescribed internal pressure after the rim assembly, if the radius of curvature of a carcass line is set to R1 at the center part of a tread 24, R2 directly under the max. width belt edge part, and R3 at the carcass max. width position, R2>R1>R3. Further, when the carcass height from the innermost position in the tire radial direction of a carcass ply 12 is H, and the carcass max. width position height is (h), 0.45<=h/H<=0.65. Further, when the radius of curvature at the height position of 70% of the carcass max. width position height (h) is R4, R4>R3. Accordingly, the bead durability is maintained, and the reduction of the crown R through traveling is suppressed, and the eccentric abrasion resistance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a heavy-duty pneumatic radial tire in which the uneven wear resistance of the shoulder portion is improved without impairing the running property and bead durability on rough roads.

[0002]

2. Description of the Related Art Pneumatic radial tires for heavy loads, which are used in vehicles such as trucks, which have a heavy load, have good ride comfort and envelope characteristics on rough roads, and have good durability against belt cut separation. For this reason, those having an aspect ratio of 90S or more are more suitable for running on rough roads than those having an aspect ratio of 80S and are often used.

[0003]

By the way, in order to obtain various performances of the tire, the carcass shape of the tire generally has a so-called natural equilibrium shape in which the shape change of the tire before and after filling with internal pressure shows uniform bulging deformation. It has been taken.

On the other hand, as shown in FIG. 5 as an example, the carcass shape in the conventional pneumatic radial tire 100 for heavy loads having the flatness of 90S, 100S, etc., has a carcass ply end failure at the bead portion and a belt end separation. The carcass 12 has a radius of curvature at the center of the tread 26 when the rim is assembled and filled with the regular internal pressure.
1. When R2 is set just below the belt end portion having the maximum width, the relationship between R1 and R2 is set to R1> R2.

As the carcass line is filled with internal pressure, the carcass line is deformed so that the vicinity of the center of the arc of the large radius of curvature is convex toward the outside of the tire, and the adjacent small radius of curvature is inside the tire. It tends to deform so as to be depressed. That is, in the conventional heavy-duty pneumatic radial tire 100, when the internal pressure is filled, the carcass line is in the tire radial direction outward (direction of arrow A in FIG. 5) near the equator plane.
Between the carcass line maximum width position 12C and the bead portion 16 moves to the outside of the tire (direction of arrow B in FIG. 5), and the area immediately below the end of the belt moves to inside of the tire (direction of arrow C in FIG. 5).

This makes it possible to apply an appropriate compressive stress to the folded end of the carcass ply under the filling internal pressure, prevent the ply end from being damaged, and increase the belt tension in the tread portion to increase the belt tension between the belt layers. It was attempted to reduce the distortion and prevent the separation at the belt end.

In the conventional tread 26 of the heavy duty pneumatic radial tire 100, the diameter on the shoulder side tends to be smaller than the diameter on the equatorial plane when the internal pressure is filled, but not so much when the tire is new. , There was no particular problem.

However, the crown radius is gradually reduced according to the running amount, and the rectangular ratio of the ground contact shape is reduced accordingly, and the shoulder side portion of the tread 26 is dragged to the road surface, resulting in shoulder drop wear. It has been found that so-called uneven wear occurs.

In consideration of the above facts, the present invention provides a heavy-duty pneumatic radial tire capable of suppressing the diameter reduction of the crown radius due to running and improving the uneven wear resistance while maintaining the bead durability. That is the purpose.

[0010]

According to the present invention, the radius of curvature of a carcass line is set in a pneumatic radial tire for heavy loads having an aspect ratio of 90 series or more with a rim assembled and filled with an internal pressure of 10% of a specified internal pressure. R in the center of the tread
1, R2 immediately below the end of the belt having the maximum width, and R3 at the carcass maximum width position, the relationship between R1, R2, and R3 is R2>R1> R3, and the carcass from the tire radial innermost position When the height is H and the carcass maximum width position height from the carcass radial innermost position is h, the relationship between H and h is 0.45 ≦ h / H ≦ 0.65. I am trying.

[0011]

According to the pneumatic radial tire for heavy loads of the present invention, the belt having the maximum radius of curvature of the carcass line is R1 at the center of the tread in a state where the rim is assembled and the internal pressure of 10% of the specified internal pressure is filled. When R2 is just below the end and R3 is at the carcass maximum width position, the relationship between R1, R2 and R3 is R2>R1> R3, the carcass height from the tire radial innermost position is H, and the carcass height is When the carcass maximum width position height from the innermost position in the tire radial direction is h, the relationship between H and h is 0.45 ≦ h / H ≦ 0.65.
Therefore, when the normal internal pressure is filled, the carcass line is deformed so that a portion immediately below the end of the belt having the largest radius of curvature becomes convex toward the outside of the tire. In addition, the carcass line is deformed so that the vicinity of the center of the tread with the next largest radius of curvature immediately below the belt edge is convex toward the outside of the tire, and there is almost no change near the position of the maximum width of the carcass with the smallest radius of curvature. Or, it deforms so as to dent inside the tire. Therefore, when the heavy duty pneumatic radial tire of the present invention is filled with a regular internal pressure, the crown shape has a tendency to be flattened as compared with the conventional one, and the crown shape is the same even when the running amount is increased. It has a tendency of flattening, and in actual running, the difference between the diameter of the shoulder side of the tread and the diameter of the equatorial plane is suppressed from increasing, and the shoulder side portion of the tread is dragged with respect to the road surface. This is suppressed, and the occurrence of uneven wear is suppressed. That is, the rectangular ratio of the ground contact shape of the tread is suppressed, and the uneven wear resistance is improved as compared with the conventional pneumatic radial tire for heavy load.

When h / H is less than 0.45,
The tensile strain at the end of the carcass ply becomes large, which may cause separation. When it exceeds 0.65, the growth becomes insufficient.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

In the heavy-duty pneumatic radial tire 10 of the present invention shown in FIG. 1, the carcass ply 12 extending radially is a carcass cord arranged in a direction orthogonal to the tire circumferential direction. It is composed of a coating rubber covering this.

Both end portions of the carcass ply 12 in the tire width direction are folded back around the pair of bead cores 14 from the inner side to the outer side in the tire axial direction to form folded end portions 12A.

In the bead portion 16 near the bead core 14, a steel cord protective layer 18 is adjacently arranged on the side opposite to the carcass ply 12. The steel protective layer 18 is a steel cord covered with a coating rubber.

Further, an organic fiber protective layer 20 and an organic fiber protective layer 22 are arranged adjacent to each other on the opposite side of the steel cord layer 18 from the carcass ply 12. The organic fiber protective layers 20 and 22 are formed by coating an organic fiber cord such as nylon with a coating rubber.

On the other hand, on the outer side in the tire radial direction of the carcass ply 12, at least three belt layers 24 are formed.
Is provided, and a tread 26 is provided on the outer side of the belt layer 24 in the tire radial direction. A predetermined tread pattern (not shown) is formed on the tread 26.

In the heavy duty pneumatic radial tire 10 having such a structure, the radius of curvature of the carcass line is R1 at the center of the tread 24 (the center of curvature is the tire with the tire being filled with 10% of the normal internal pressure). (Equatorial plane), R2 immediately below the end of the belt having the maximum width, and R3 at the carcass maximum width position, the relationship between R1, R2, and R3 is R2>R1> R3, and the carcass ply 12 When the carcass height from the innermost position in the tire radial direction is H and the carcass maximum width position height is h, the relationship between H and h is 0.45 ≦ h / H ≦ 0.65.
Further, when the radius of curvature at the height position 70% of the carcass maximum width position height h is R4, the carcass line is R
The relationship between 4 and R3 is R4> R3.

The relationship w / W between the distance w of the boundary point a between R1 and R2 from the equatorial plane of the tire and the maximum width t of the tread is:
The condition is 0.6 ≦ w / W ≦ 0.9. The maximum tread width W as used herein refers to the dimension in the direction along the tire axis from the tire equatorial plane to the shoulder end on one side in the tire axial direction.

The heavy duty pneumatic radial tire 10 of this embodiment has a tire size of TBR-10.00R20 and an aspect ratio of 100%.

In the heavy duty pneumatic radial tire 10 of this embodiment, the radius of curvature of the carcass line is R1.
240mm, R2 280mm, R3 80mm, R4 1
The carcass height H is 278 mm and the carcass maximum width position height h is 166 mm. Therefore,
In the heavy duty pneumatic radial tire 10 of the present embodiment,
h / H is set to 0.597.

In the heavy-duty pneumatic radial tire 10 of this embodiment, the dimension w from the tread center CL at the intersection a of the radii of curvature R1 and R2 is 140 mm, and the maximum width W of the tread is 200 mm. Is. Therefore, the heavy-duty pneumatic radial tire 1 of the present embodiment
At 0, w / W is 0.67.

When the maximum width of the carcass is S,
The maximum width dimension W of the tread, W / S, is 0.6.
It is preferable that ≦ W / S ≦ 0.75.

Next, the operation of this embodiment will be described. In the heavy-duty pneumatic radial tire 10 of the present embodiment, the radius of curvature of the carcass line is R1 at the center of the tread 26 and R2 immediately below the belt end having the maximum width in a state of being filled with 10% of the normal internal pressure. , R3 at the carcass maximum width position, the relationship between R1, R2 and R3 is R2>R1> R3
When R4> R3, the carcass height is H, and the carcass maximum width position height is h, the relationship between H and h is 0.45 ≦ h / H ≦ 0.65. When the internal pressure is filled, as shown in FIG. 1, the carcass ply 12
Means that the center portion of the tread 26 is deformed outward in the tire radial direction (direction of arrow A in FIG. 1) and the carcass maximum width position 12A is deformed inward in the axial direction of the tire (direction of arrow D in FIG. 1), along with this, the shoulder side of the tread 26. The vicinity of the end portion is deformed to the outside of the tire (direction of arrow E in FIG. 1). Further, the portion between the maximum width position 12A of the carcass and the bead portion is deformed toward the outside of the tire (direction of arrow B in FIG. 1).

Therefore, in the pneumatic radial tire 10 for heavy load of the present embodiment, the crown shape in the tire cross section tends to be flattened by being filled with the normal internal pressure, that is, the crown radius due to the running growth. Since it is possible to suppress the diameter reduction, the difference in diameter between the center side portion and the shoulder side portion from the tire axis is small on the tread surface of the tread 26, and the tread 26 caused by the diameter difference on the shoulder portion side of the tread 26. Uneven wear at both ends can be greatly suppressed as compared to the conventional pneumatic radial tire for heavy load.

When the relationship h / H between the carcass height H and the carcass maximum width position height h is less than 0.45, the portion displaced outward in the tire axial direction (the portion R4) is the ply end 12.
Since it gets too close to B, a tensile strain is applied to the ply end 12B, so that the ply end 12B is likely to be damaged by the ply end separation. On the other hand, the tread with h / H exceeding 0.65 approaches the carcass shape of the conventional pneumatic radial tire for heavy load, and the change of the shoulder portion to the outer side in the tire radial direction due to the internal pressure filling is insufficient, and the shoulder drop wear is caused. Not effectively improved.

Furthermore, when the distance w of the boundary point a between R1 and R2 from the equatorial plane of the tire and the maximum width W of the tread are represented by w and W, if w / W is less than 0.6, the radius of curvature R2 is large. Since the area is too wide and the tension is dispersed, it is not possible to effectively reach the outer side of the tire in the radial direction of the tire due to internal pressure filling, and it is not possible to sufficiently suppress the reduction of the radius of curvature of the crown radius due to running. On the other hand, when w / W exceeds 0.9, the carcass shape of the conventional pneumatic radial tire for heavy load approaches the carcass shape, and the change of the shoulder portion to the outer side in the radial direction of the tire due to the internal pressure filling is insufficient, resulting in shoulder drop wear. Not effectively improved.

[Test Example] The heavy-duty pneumatic radial tire 10 of the present example and a conventional heavy-duty pneumatic radial tire were assembled into rims, respectively, and the change rate of crown radius, the step-down amount at the shoulder side end of the tread, and The durability of the bead portion was tested.

The conventional pneumatic radial tire for heavy load used in the test has a tire size of TBR-10.00R2.
0 and the flatness rate is 100%. Further, in the conventional pneumatic radial tire for heavy load, the radius of curvature of the carcass line at an internal pressure of 10% is R1 of 400 mm and R2 of
Is 80 mm, R3 is 120 mm, R4 is 100 mm, the carcass height H is 278 mm, and the carcass maximum width position height h is 160 mm. Further, the dimension w from the tread center CL of the intersection a of the radius of curvature R1 and the radius of curvature R2.
Is 130 mm, and the dimension W from the tread center CL to the end of the belt layer 24 is 190 mm.

The rate of change in crown radius is determined by assembling each test tire on a rim, filling the tire with regular internal pressure, and mounting the tire on an actual vehicle to run the load at 100% of the specified load. The curvature of the Earl was measured. The relationship between the change rate of the crown radius and the traveling distance is shown in the graph of FIG. The vertical axis of the graph represents the rate of change of crown radius (100 when the product is new), and the horizontal axis represents the traveling distance. Also, tread 2 after the test
The running growth amount in the cross section of No. 6 is shown in the graph of FIG.

As for the step-down amount, similarly, each test tire is assembled on a rim, filled with a regular internal pressure, and mounted on an actual vehicle, and the load is run at 100% of the specified load.
The amount of wear of both ends of the tread from the time of new article was measured for each predetermined traveling distance. The relationship between the step-down amount and the traveling distance is shown in the graph of FIG. The vertical axis of the graph represents the amount of wear of both ends of the tread from the time of new product, and the horizontal axis of the graph represents the travel distance.

Further, regarding the durability of the bead portion, similarly, each test tire was assembled on a rim, filled with a regular internal pressure and mounted on an actual vehicle to run, and the traveling distance up to damage to the bead portion (ply end separation) was measured. However, it is an index display with the mileage when the conventional pneumatic radial tire for heavy load causes damage to the bead portion as 100. The test results are shown in Table 1 below. In addition, in Table 1, the traveling distance is 0 km.
The crown radius at the time point and at the time of 20,000 km, and the step-down amount (wear amount) of the tread end portion at the time of the traveling distance of 50,000 km are also described.

[0034]

[Table 1]

From the test results shown in the graphs of FIG. 2 to FIG. 4, the pneumatic radial tire for heavy load of the present invention has a smaller rate of change in crown radius as compared with the conventional pneumatic radial tire for heavy load, and the tread of tread It is clear that the amount of step down at the shoulder end is small,
Further, from the test results shown in Table 1 above, it is clear that the durability of the bead portion of the pneumatic radial tire for heavy load of the present invention is improved as compared with the conventional pneumatic radial tire for heavy load.

[0036]

As described above, since the pneumatic radial tire for heavy loads of the present invention has the above-mentioned constitution, while maintaining the bead durability, it is possible to suppress the diameter reduction of the crown radius due to running and to prevent uneven wear. It has an excellent effect that the property can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heavy duty pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a change rate of crown radius and a traveling distance.

FIG. 3 is a graph showing a running growth amount in a cross section of a tread.

FIG. 4 is a graph showing a relationship between a step-down amount and a traveling distance.

FIG. 5 is a cross-sectional view of a conventional heavy-duty pneumatic radial tire.

[Explanation of symbols]

 10 Pneumatic radial tire for heavy load 12 Carcass ply

Claims (1)

[Claims] 1. A pneumatic radial tire for heavy loads having an aspect ratio of 90 series or more, the radius of curvature of the carcass line is R at the center of the tread with the rim assembled and filled with an internal pressure of 10% of the specified internal pressure.
1, R2 immediately below the end of the belt having the maximum width, and R3 at the carcass maximum width position, the relationship between R1, R2 and R3 is R2>R1> R3, and the carcass from the innermost position in the tire radial direction of the carcass. When the height is H and the carcass maximum width position height from the carcass radial innermost position is h, the relationship between H and h is 0.45 ≦ h / H ≦ 0.65. Pneumatic radial tires for heavy loads.